SIMBAD references

The [Zr/Ti] ratio for a large sample of Galactic S stars has been determined using high-quality, high-resolution spectra. The pattern of Zr enhancements in intrinsic and extrinsic S stars is found to differ, and the [Zr/Ti] ratio in the extrinsic S stars clearly links them to the strong barium stars. In addition, the pattern of [Zr/Ti] ratios seems to indicate that the progression of spectral type M to MS to S to SC is due largely to an increase in the abundance of s-process elements and not solely to a changing C/O ratio as claimed by some investigators (such as Scalo and Ross).